Prior to being appointed to the U.S. Court of Appeals for the Federal Circuit by President Obama in 2010, Judge O'Malley was appointed to the Northern District of Ohio by President Clinton in 1994, where she remained until her 2010 appointment to the Court of Appeals. Before she was appointed to the federal bench, Judge O'Malley served as First Assistant Attorney General and Chief of Staff to Ohio Attorney General Lee Fisher from 1992 until 1994. Judge O'Malley also practiced law at Porter, Wright, Morris & Arthur, where she became a partner in the firm's litigation department, and she also practiced at Jones Day. She is currently Case Western Reserve Law School's Distinguished Visiting Jurist, where she teaches patent litigation and regularly serves as a guest lecturer in areas such as trial practice, evidence, and criminal procedure.

Kathleen M. O'Malley is on the Advisory Board for The Sedona Conference.